Investigation of duobinary modulation implementations for use in wavelength switched networks

We investigate the use of different duobinary modulation implementations in a wavelength-switched network operating at 10 Gb/s. The work specifically focuses on two methods of generating duobinary: phase shaped binary transmission (PSBT) which uses both a phase modulator and a Mach-Zehnder modulator (MZM) and enhanced PSBT (EPSBT) which uses two MZM´s. We evaluate the benefit associated with modifying the extinction ratios of both implementations in order to optimise the signal for either short- (low back-to-back penalty) or long-distance transmission (good dispersion tolerance). The tolerance of these implementations to impairments associated with the settling of tunable lasers <;200 ns after switching (such as wavelength error and linewidth broadening) are also investigated and the associated penalties are found numerically.